The White-cheeked Gibbon, also called the Northern White-cheeked, is native to Vietnam, Laos and part of China and is critically endangered in the wild.
The Southern White-cheeked Gibbon, from the same countries, was split as a separate species (Nomascus siki) in 2001.
Only the male (above), which is black, has white cheeks.
Hear no evil
The female (above) is honey-coloured with a black face and cap but no white cheeks.